1. Field of the Invention
The present invention relates generally to screwdrivers, and in particular to methods, devices and systems for feeding screws automatically to an electric screwdriver.
2. Description of the Related Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA). The spindle motor includes a spindle motor hub that is rotatably attached to the disk drive base.
Advances in the hard disk drive industry have led to the incorporation of disk drives into a variety of hand held devices, such as music players, cameras and PDAs. The small size of such devices has led to a corresponding reduction in the form factor of high capacity hard disk drives. Conversely, the ability of manufacturers to introduce ever smaller drives has led to their incorporation in ever widening classes of electronic devices and to the development of entirely new classes of devices. Form factors have steadily shrunk from 5.25″, 3.5″, 2.5″, 1.8″ and now to 1 inch and smaller drives.
As a result of such continuing miniaturization, many of the constituent components of the drives have become too small to be consistently, speedily and reliably handled by human hands. For example, screws that are used in such small form factor drives include so-called M1 screws, which have a diameter of just 1 mm and a head height of just 0.2 mm. These screws are difficult to pick up, couple to a screwdriver and drive into a selected threaded hole in a disk drive. Such problems have led to the development of electric screw driving machines. Many existing electric screwdrivers in the factory require the operator to manually or vacuum pick the screws from a shaker tray before driving them on designated fixtures. That is, before driving a screw, the operator must swing the electric screwdriver over to the shaker tray. After the electric screwdriver is in position over the shaker tray, the operator must cause a screw to couple to the bit of the electric screwdriver and swing the electric screwdriver and coupled screw in position over the disk drive to drive the screw therein. After the screw has been driven, the operator must once again swing the electric screwdriver over the shaker tray to couple another screw to the electric screwdriver. The repetitive process of swinging the electric screwdriver over the shaker tray, picking up a screw and swinging the screwdriver back over the disk drive (which is sometimes called a “pick-and-place” process) is time consuming (and, therefore, decreases the manufacturing line's yield). Improving upon the conventional method of picking up screws from a shaker tray would decrease the screw driving cycle time, as well as operator fatigue.
Electric screwdrivers with automatic screw feeding systems do exist, but typically rely on a blow feed system to feed the screws to the screwdriver. Such blow feed systems use a blast of air to carry the screw from its source to a position in which it may be engaged by the screwdriver's bit. This blast of air typically escapes from the screwdriver in the vicinity of the screwdriver's bit and may carry particulate matter and other contaminants to the work area. Electric screwdrivers featuring blow feed systems are, therefore, unsuitable for environments in which it is desired to minimize such contamination, such as clean room environments, for example. What are needed, therefore, are electric screwdrivers having automatic screw feeding mechanisms that are suitable for use in clean room environments and other environments in which it is desired to minimize contamination.